Process for dewaxing oils



Patented Nov. 16, 1937 PATENT FF CE rnoonss 7 FOR DEWAXING OILS Charles Douglas Barnes, Long Beach, and. Marcellus T. Flaxman, Wilmington, Calif., assignors to Union Oil Company of California, Los Angeles, Calif., a corporation of California No'Dratving. Application February 24, 1936,;

- 7 Serial No. 65,414

10 Claims. 01. 196-19) The present invention relates to improvements in the art of separating wax from wax -bearing: oil, such as lubricating oil distillates or residues. More particularly, the invention pertains to a method in. which certain materials areadded to the wax-bearing oil tocondition it so that the wax may be more readily. separated from the oil. This invention is also applicable to a process forthe separation of oilfrom waxes, such as slack wax, wax cakes, etc. v

Manylubricating oil fractions contain relatively large quantities of wax which impart a'high pour point to the oil and thereby render these oils less desirable as motor lubricantsas they are solid and will not flow at ordinary temperatures. 7

In order to make these oils suitable foruse at ordinary temperatures, it is necessary to remove the wax'contai'ned' in the oil. Thisis usually accomplished'by'addin'g a suitable diluent to the wax-bearing oil, "chilling the diluted oil to a temperature sufliciently low to congeal the wax content andthen removingthe wax from the diluted oil by settling, centrifuging, or filtering.

' It is. well known that an efiicient dewaxing process isone in which thezwax may be removed as rapidly as is possible to produce a large amount of dewaxed oil having a reasonably low pour point and to produce a wax reasonably free from oil, that is, having ,a high melting point. In other words, it is desirable to separate the wax from the oil, for example, by filtration, at a very high rate and yet to recover as much wax-free oil as is possible from the original stock In many of the processes now'in use, it ispossible to produce oils oflow pour point; however, the yield of oil recovered is unsatisfactorilylow and the melting point of the separated wax is low, indicating that a' large amount of oil, is retained'in the wax. Also, the rate atwhich the wax is separated from the oil by filtration, for example, is also low.

We have discovered thatthe wax contained in oils may be more readily separated by mixing the wax-bearing" oil with certain materials which render thewax more readily separable from the 'oil. Hereinaften'the materials which we desire to employ to conditionthe wax present in the wax bearing oil in order to effect more ready separation of the wax from the oil will be referred to as wax separation aids. V

We have discovered wool grease and lanolin to be quite efiective as wax separation aids in the dewaxing of waxy oils. We have further discovered that oxidized wool grease and oxidized lanolin tobe even more effective as'wax separation aids than the unoxidized materials. The

reason'for the unexpected activity ofithe afore'-- mentioned wax separation aids in dewaxing oils is not definitely known but it is known that when a small amount of either the oxidized or unoxidized material is added to the'oil to be dewaxed, an improvement is obtained with respect to the;

. yield of dewaxed oil", filter rate, and melting point of the separated wax as compared to similar de- Waxing conditions when no wax separation aid is employed. One explanation for this phenomenon may be that since the aforementioned wax separation aids contain material amounts of cholesterol and derivatives related to cholesterol, it is possible that such ingredients are largely. responsible for the potency of the aforementioned wax separation aids.

Wool grease, as is well known, is the grease which naturally protects the wool while on sheep or other animals and which amounts to about 20% of the fleece. fleece byscouring the fleece with a detergent solution such as, for example, a soap and sodium carbonate solution o'r'by other means utilizing a hydrocarbon solventsuch as a high test gasoline or naphtha which has no effect upon the wool.

In the latter case, the solution of naphtha and grease is run into a still whereupon the greasy, solvent is heated to. drive. off the gasoline or naphtha. The grease which remains in the still is washed with warm water and dried by blowing with warm air. Wool grease is sometimes referred to in the United States as degras. The following are the approximate characteristics of wool grease as recovered by the aforementioned process:

Melting point 97 to 108 F. Moisture content 2 to 2 Ash 0.1 to 0.8% Free fatty acid (figured as oleic acid) about 9 to 10% Saponifiable matter about Specific gravity at 60 F; .967 Saponiflcation number 113 to 123 Acid value not over 20.9% Viscosity at 210 (Tagliabuel. 284 to 292 4 Flash point 3'72 to 390 F. Fire test -1, 527 to 536 F. Cold test 94 F. Iodine value -1 about 27 50 In general, the oxidized wax separation aids may be produced by subjecting the unoxidized materials aforementioned to the action of an oxygen containing gas, such as air, oxygen, ozone or hydrogen peroxide, preferably at elevated tem- This may be removed from the 6' dation will vary with the type of material treated] The oxidation consists in heating the wool grease, for example, to a temperature of about 350 F. and introducing air, oxygen, ozone or hydrogen peroxide into the charge until sufiicient oxidation has taken place to render the material active as a wax separation aid and yet retain its compatibility with the oil to bezdewaxed. In one;-

case, oxidation of wool grease was effected by introducing air While maintaining the, charge at about 340 F. for a period of about 200 hours.

The oxidation reaction with air, oxygen or ozone, or with hydrogen peroxide, may be aided when the oxidation reaction is carried out in the presence of catalysts. Catalysts which may be employed with benefit for this purpose are metal chlorides, such as the chlorides of iron,

zinc, tin, aluminum, metal soaps, such as the naphthenates, oleates, stearates, ricinoleates, palmitates of sodium, copper, magnesium, aluminum, cobalt, and iron. I

In carrying out the dewaxing process, a small amount, i. e. 0.3% to 1% by volume of the oxidized or unoxidized wax separation aid is mixed with or dissolved in the wax-bearing oil, after which the mixture is chilled to a:'su-fficiently low temperature to precipitate or solidify the wax contained in the oil. The solidified wax may then be separated from the chilled mixture by settling, centrifuging, or filtering. The added wax separation aid will be precipitated and removed along with the Wax. If desired, a concentrated oil solution of the wax separation aid may be produced by first mixing or dissolving a small quantity of the waxy distillate to be dewaxed with the wax separation aid at an elevated temperature, such as, for example, about 350 F. The concentrated solution may then be added to the waxy distillate in an amount as to incorporate the desired amount of the wax separation aid into the oil to be dewaxed.

In many cases, it is desirable to dilute the mixture of wax-bearing oil and Wax separation aid with a suitable diluent prior to the chilling step in order to render the oil fluent at the dewaxing temperature. As diluents, we preferably employ liquefied normally gaseous hydrocarbon such as ethane, ethylene, propane, propylene, butane, butylene, or mixtures thereof or we may employ such light hydrocarbons suchas 'pentane, hex-,

of these hydrocarbons with the aforementioned hydrocarbons.

The use of a liquefied normally gaseous diluent, such as liquid propane, is preferred, since in addition to having the property of retaining less wax in solution at low temperatures, it may be employed to produce the necessary degree of refrigeration to precipitate the wax from the solution by vaporizing a portion of the liquefied normally gaseous material from the diluted oil under reduced pressure.

It is thus an object of our invention to improve dewaxing characteristics of wax-containing oil by adding a small quantity of an oxidized or unoxidized wool grease or lanolin to the oil to be dewaxed.

A further object of our invention resides in dissolving the wax-bearing oil to be dewaxed and the aforementioned wax separation aid in a suitable'diluent, chilling the mixture to congeal the wax content and separating the congealed Wax and oxidized wax separation aid from the diluted oilby filtration, centrifuging or settling.

Many specific objects, features and advantages ofour invention will become apparent to those skilled in the art as the description of our invention proceeds in connection with the specific examples given below which are not to be considered as limiting our invention but merely illustrative of methods of carrying it out.

In one run, about 350 grams of the wool grease having the characteristics aforementioned Was heated in a still to a temperature of about 200 F. and was blown gently with air until approximately the entire moisture content was distilled from the material. Thereupon, the temperature was increased to approximately 340 F. and was maintained at such temperature for approximately 200 hours during which time air was introduced into the charge at a rate of approximately 10 liters per hour. This resulted in the production of an oxidized wool grease which had the following characteristics:

Acid number 23.0 Saponification number 147 Gravity at 60 F 0.991

The oxidized wool grease was mixed in a closed vessel with an SAE 20 waxy lubricating oil distillate obtained by the vacuum distillation of a Santa Fe Springs crude oil. The admixture was accomplished at a temperature of about 300 F. and in an amount as to incorporate approximately 0.5% by weight into the waxy distillate. The resultant mixture was then diluted with approximately 3.0 volumes of liquid propane under super-atmospheric pressure to one of the oil containing the wax separation aid. The temperature of the resultant mixture was about F. and the pressure was about 250 lbs. per square inch. The mixture of waxy lubricating oil, propane, and oxidized wool grease was then chilled externally at a rate of approximately 3 F. per minute until a temperature of approximately -40 F. was attained, the refrigeration being accomplished by vaporizing under gradually reduced pressure a portion of propane in a jacket surrounding the chilling vessel. The chilled slurry of propane, lubricating oil and solidified Wax and wax modifier was then filtered under a pressure of approximately 25 lbs. per square inch in order to effect the separation of the precipitated wax and wax modifier from the chilled propane solution of lubricating oil. The filter rate was approximately 16.6 gallons per square foot of filter surface per hour based on propanefree oil. After distilling the filtrate in order to remove propane, a yield of approximately 84.0% by volume of dewaxed oil was recovered having a pour point of 5 F. The separated wax had a melting point of about 127 F. as determined by the Ubbelohde method.

indicate that this type of wax separation aid is 7 only 117 F. The filter rate was only 2.4 gallons .per square foot per hour.

quite active in dewaxing oils when it is compared with a blank run wherein no wax separation aid is employed. A blank run on the sameoil using the same amount of propane and carried out under the same conditions as above, showed that only approximately 64.8% by volume of oil was obtained having a pour point of 10 'F. The wax separated from the oil had a melting. point of In another run, unoxidized dehydrated wool grease was substituted for the oxidized wool The results obgrease in the above example. tained indicate that this wax separation aid while not quite as potent as the oxidized material was sufiic'iently effective to warrant its use in commercial dewaxing processes. In this run, the filter rate was approximately 11.5 gallons per square foot per hour; the yield of dewaxed oil was 79.6% by volume with a pour point of 10 F.

while the separated wax had a melting point of about 126 F.

Another run similar to the above but substituting oxidized lanolin which is a highly refined wool grease showed results as follows: The filter rate was approximately 19.3 gallons per square foot per hour; the yield of dewaxed oil was 82.2% by volume having a pour point of 5.F. and the melting point of the separated wax was about It will be observed that the foregoing description of our invention is not to be considered as limiting as many variations thereof maybe made by those skilled in the art within the scope. of the following claims. r

We claim: 1. A process for conditioning oils preparatory to the separation of wax therefrom which comprises mixing said wax and oil with a wax separation aid containing cholesterol.

2. A process for separating wax from wax-oil mixtures which'comprises mixing the wax-oilmixture with a wax separation aid containing cholesterol, chilling'the mixture to solidify the wax content and separating the solidified wax from the oil.

3. A process for separating wax from wax-oil mixtures which comprises mixing the wax-oil mixture with a wax separation aid containing cholesterol and a diluent, chilling the mixture to solidify the wax content and separating the solidified wax from the oil. r

4. A process as in claim-2 in which the wax separation aid comprises wool grease.

5. A process as in claim 2 in which the wax separation aid comprises lanolin.

6. A process as in claim 3 in which the diluent 9. A process as in claim 3 in which the wax separation aid comprises wool grease and the diluent comprises a liquefied normally gaseous hydrocarbon.

10. A process as in claim 3 in which the wax separation aid comprises lanolin and the diluent comprises a liquefied normally gaseous hydrocarbon. V g

CHARLES DOUGLAS BARNES. MARCELLUS T. FLAXMAN.

the wax 

